The present invention relates to static controlled active power conditioners.
The present invention extends the field of application of active power conditioners to buck/boost voltage regulation, phase correction, power factor correction, as well as active filtering between a source and a load. The invention is also applicable to multi-phase systems for active filtering and unbalanced load compensation.
The active power conditioner system according to the present invention is derived from the active power filter mounted between a power source and a load for ripple elimination as disclosed in U.S. Pat. No. 3,825,815 of July 23, 1974. The active power filter is a static controlled device connected between the power source and the load to generate a synthetic ripple matching the ripple to be opposed and eliminated. Control is by pulse-width modulation of static switches operating at a high carrier frequency, the carrier being easily removed by filtering.
With a nearly ideal filter characteristic, the active power filter allowed only power of fundamental frequency to flow from the source to the load. The active power filter embodies storage elements, e.g., inductors, or capacitors, which are capable of storing energy in the form of direct current under direct current voltage. The active power filter of the prior art when used as an active power conditioner was only capable of supplying, or absorbing, real power with such inductors, or capacitors, to the extent that losses were compensated. Nevertheless, such active power filters were also used to generate reactive currents with such DC inductors, or DC capacitors, at the fundamental frequency, with either leading or lagging reactive power.
The present invention makes use of the active power filter in such a way that an active power conditioner system is formed having distinct advantages and capable of performing more functions than the aforestated prior art active power filter.